\documentclass[11pt]{article}
\usepackage{subscript}
\usepackage[margin=1in]{geometry}
\setlength{\parindent}{0pt}
\setlength{\parskip}{4pt}
\pagestyle{empty}

% relational
\newcommand{\select}{$\sigma$}
\newcommand{\project}{$\pi$}
\newcommand{\rename}{$\rho$}
\newcommand{\join}{$\bowtie$ }

% sets
\newcommand{\union}{$\cup$ }
\newcommand{\inter}{$\cap$ }
\newcommand{\diff}{$-$ }
\newcommand{\cross}{$\times$ }

% extended
\newcommand{\nodup}{$\delta$}
\newcommand{\group}{$\gamma$}
\newcommand{\order}{$\tau$}
\newcommand{\limit}{$\lambda$}

% logic
\renewcommand{\and}{\textsc{and} }
\renewcommand{\or}{\textsc{or} }
\renewcommand{\not}{\textsc{not} }

% null
\newcommand{\isnull}{\textsc{is null}}
\newcommand{\notnull}{\textsc{is not null}}

\begin{document}

% Examples from http://www.cs.duke.edu/~junyang/ra/
% replace _'s after select, project, and join with \textsubscript
% escape all other _'s (i.e., they're part of a variable name)

\select\textsubscript{name = 'Amy' \or name = 'Ben'} Drinker

\project\textsubscript{bar, beer}(\select \textsubscript{bar = 'Talk of the Town'} Serves)

Drinker \join\textsubscript{name = drinker} Frequents

Drinker \join \rename\textsubscript{name, bar, times\_a\_week}(Frequents)

\rename \textsubscript{name1, address1} Drinker \cross \rename \textsubscript{name2, address2} Drinker

\bigskip

Drinker \join Frequents

Drinker \cross Frequents

Drinker \union Drinker

Drinker \diff Drinker

Drinker \inter Drinker

\bigskip

\order{pass\_rate, school} (\select\textsubscript{(school \notnull) \and (85 $<$ pass\_rate)} (\project\textsubscript{school, pass\_rate} (\select\textsubscript{test \isnull} (Test Data))))

\end{document}
